using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var teste = new Foo { details = new List<Detail>() } ;

        teste.details.Add(new Detail { data = "oi"} );

        Exec(teste);

    }

    public static void Exec(FooBase obj){

        var a = (IBoo<Detail>)obj;      

        Console.WriteLine("Count: " + a.details.Count);

        var b = (IBoo<IData>)obj;       

        Console.WriteLine("Count: " + b.details.Count);

    }

    public interface IBoo<T> {

        List<T> details {get;set;}

    }

    public interface IData{

        string data {get;set;}

    }

    public class FooBase{

        public string baseValue {get;set;}

    }

    public class Detail: IData {

        public string data {get;set;}

    }

    public class Foo : FooBase, IBoo<Detail>{

        public List<Detail> details {get;set;}

    }

    public class Foo2 : FooBase, IBoo<Detail>{

        public List<Detail> details {get;set;}

    }

}